1. Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of forming a silicon-on-insulator (SOI) device using a large angle implant of oxygen in the fabrication of integrated circuits.
2. Description of the Prior Art
In a first method of forming an epitaxial layer on an oxide layer, shown in FIG. 1, a silicon dioxide layer 2 is formed on the surface of the silicon substrate 1. Epitaxial silicon layer 3 is deposited overlying the silicon oxide layer 2. Crystal defects 4 may be found within the layer 3 because of the different structures of the crystal lattices of silicon and silicon dioxide.
FIG. 2 illustrates a second method of forming an insulating layer over an oxide layer. Silicon oxide layer 2 is formed on the surface of a silicon substrate 1. A layer of silicon 5 is deposited overlying the silicon oxide layer. Oxygen ions 6 are implanted at high energy and high dosage into the silicon layer and then annealed to form silicon dioxide layer 2 under the silicon layer 5. Some damage 7 may occur within the silicon layer 5 because of incomplete annealing.
In their article, "Fully Depleted Lean-Channel Transistor (DELTA)," by Hisamoto et al, IEEE Electron Device Letters, Vol. 11, No. 1, January 1990, the authors present a silicon-on-insulator device in which the oxide is formed in a furnace and the silicon is protected by a silicon nitride layer.
Ion implantation of dopants has been used by a number of workers in the art in the formation of isolation regions. U.S. Pat. No. 4,912,062 to Verma uses vertically implanted Sb, As, P, or B dopants to enhance oxide growth without a mask during the oxidation step. U.S. Pat. No. 4,975,126 to Margail et al shows vertical implantation of oxygen ions into a silicon wafer and heating to form an isolation layer of silicon dioxide within the wafer without a mask during oxidation anneal. The article, "Selectively Implanting Oxygen Isolation Technology (SiO)" published in Electronics Letters, May 9, 1985, Vol. 21, No. 10, pp. 442-443, shows vertical ion implantation of oxygen at the surface of a silicon wafer using a silicon nitride mask during oxidation.
Large tilt-angle implant processes have been used by a number of workers in the art. Related U.S. patent application Ser. No. 08/160,243, filed on Dec. 2, 1993 uses a large tilt-angle implant process to form a buried subcollector region in the fabrication of bipolar transistors.